Simplified proximity fuze and/or howitzer shells

ABSTRACT

A novel electrical system relating to a proximity fuze which provides rectifying and capacitive amplification as a substitute for tubes.

United States Patent John 1. Hopkins Silver Spring, Md.;

Robert ll. Thayer, Chicago, Ill.

Feb. 27, 1948 Oct. 12, I971 The United States of America as represented by the Secretary of the Navy [72] Inventors [2 I Appl. No. [22] Filed [45] Patented [73] Assignee [54] SIMPLIFIED PROXIMITY FUZE FOR MORTAR AND/OR I-IOWITZER SHELLS 2 Claims, 1 Drawing Fig.

[52] US. Cl l02/70.2 P, 343/7 PF [5 1] Int. (l F42c 13/04 [50] Field oiSearch 3 l5/352; 250/27, 27.3; l02/70.2 P; 343/7 PF [56] References Cited UNITED STATES PATENTS 2,072,278 3/1937 Schode 250/27.3 2,336,768 12/1963 Six et al. 250/27 Primacy Examiner-Rodney D. Bennett Attorneys-G. J. Rubens and Claude Funkhouser ABSTRACT: A novel electrical system relating to a proximity fuze which provides rectifying and capacitive amplification as a substitute for tubes.

A-tnmary IBOv m me B-bcHary 22 I SIMPLIFIED PROXIMITY FUZE FOR MORTAR AND/OR HOWITZER SHELLS .The present invention relates to a proximity fuze, designed more particularly for use with projectiles such as mortar or howitzer shells, that attain only relatively small altitudes, in contrast to antiaircraft ammunition.

Due to the fact that such fuzes act to ignite their shells relatively close to the surface of the terrain or water over which they are fired, they need not be as sensitive as those that must operate at high altitude, and consequently the customary amplifier is not needed.

An object of the invention is to simplify the electrical system of the fuze by eliminating the amplifier.

Another object is to provide a simplified fuze having a relatively low sensitivity, which nevertheless is ample for the desired purpose.

These objects, among-others, maybe accomplished by substituting nontherrnionic rectifying devices for some of the tubes ordinarily used in the amplifier, this securing several advantages.

Due to the relative smallness of solid rectifiers when c pared with themtionic devices, these rectifier elements take much less room.

In contrast to tubes, the rectifiers also have much simpler circuits, eliminating most of the resistors and many capacitors.

The rectifiers require neither heating current nor anode and grid voltages, thus not only dispensing with many connections, butalso making it possible to reduce the electrode size of both the A-battery and the B-battery, whereby a larger number of battery plates may be accommodated in the allotted space so that a l80-volt battery is made available, in place of the 90- volt one formerly used, and this in turn increases the efiiciency and power of the oscillator triode.

The invention will be understood from the present description, and the drawing accompanying it, the single FIGURE of which illustrates one type of circuit that may be used.

The system as a whole comprises a triode V, acting in the dual role of generator of the oscillations emitted by the proximity fuze, and detector of the reflected signal received by the fun.

Power is supplied by the conventional A, B and C batteries which have a common ground, at terminals A-, B- and 0+, in the usual way.

The oscillation generating system comprises an inductance 1, an intermediate point of which is connected to the grid of V while its terminals are connected to ground conductor 2 and antenna 3, respectively. Suitable radiofrequency chokes 4, 5 are connected in the filament leads 2 and 31 of V,, as shown, while a capacitor 25 of relatively small capacitance affords a path for the high-frequency current while isolating the anode of V, from its filament with respect to the direct current source.

The triode V,, as already stated, acts also as a detector. lts output is fed through a conductor 6 to the voltage multiplier circuit, which is here shown as comprising six small rectifiers 7, 8, 9, 10, ll, 12, preferably of the selenium type, which is relatively insensitive to mechanical shock. These, as-shown, have their cathodes at the right, that is, current can flow to the right, as indicated by the arrow heads or triangles re res nting the rectifier anodes.

Suitable capacitors-l3, l4, 15, 16, 17, 18, here each 0.01 mfd. are connected as shown, three of them in wires leading from points in a conductor 19, the other three from points in the grounded conductor 2, located as shown with respect to the rectifiers.

A resistor 21, say l2,000 ohms, through conductor 6, connects the anode of V, to the conductor 22 connected to the positive terminal of the B-battery, here of 180 volts, and another resistor 20, suitably 100,000 ohms, connects said anode to the conductor 19, already mentioned.

It will be noted that all the rectifiers are connected in the same sense, and in series relationship, by means of conductors 32, 33, 34, 35, 36 and 37, so that positive impulses can pass through all, to the grid of a thyratron V,, but negative impulses cannot. It will also be seen that, beginning at the left, the ground wire 2, and the successive capacitors l3, l4, l5, l6, l7 and 18 are arranged alternately on opposite sides of the string of rectifiers.

A resistor 28, suitably l0 megohms, is connected across wires 2 and 37, and another circuit, containing in series the biasing C-battery of 6.5 volts and the resistor 29 of 3.3 megohms, is also bridged across these two wires. It will be noted that, in the closed circuit thus produced, containing re sistors 28 and 29 and the C-battery in series, a current will flow, and there will consequently be a voltage drop in resistor 29 which reduces the actual grid bias to a value usually somewhere between -45 and 5 volts. Although this circuit is apparently permanently closed, it must be remembered that all the batteries are of the deferred-action type, hence no current flows before these batteries become activated in the conventional way when the projectile is launched or fired.

A squib 27 is connected in series with a capacitor 26 of the order of l mfd., between conductor 24 leading to the anode of V,and the grounded cathode thereof. A resistor 30, shown as 5 megohms, is also bridged across said anode and cathode, and serves, in conjunction with resistor 23 of about the same value, to divide the B-voltage approximately in half, so that about volts is applied to the anode of the thyratron V,.

The operation of the circuit is as follows:

Assuming that the circuit of triode V isemitting oscillations and that a responsive oscillation is being received by reflection from a target and detected as a much-lower-frequency beat, this means that an alternating current is being fed from the anode circuit of V to the rectifier circuit. 1

If the rectifiers were perfect, and losses .could be eliminated entirely in the circuits, each rectifier would augment the received voltage by the same amount, equal to the original, so that the six rectifiers would thus multiply the input voltage by six. Actually, these ideal results are not fully realized, so that the amplification produced falls below the theoretical value of six, and this fact also limits the number of rectifiers that can be used advantageously as voltage multipliers.

An increase in the number of rectifying stages also causes an increase in the time of response, inasmuch as more capacitors must become charged, and to progressively higher voltages, before the final voltage amplification ensues. Hence, practical considerations limit the voltage increase that is attainable.

However, it is not to be assumed that six rectifiers are necessary, since fewer or more may be found desirable in specific cases. in any event, when, on approaching a target, the voltage fed by the rectifiers to the grid of V, becomes sufficient, sucli rectified voltage will reduce the original negative bias to an amount which will allow the said thyratron to fire. This firing virtually short-circuits the cathode to the anode for a brief time, during which the capacitor 26, initially charged to the full anode voltage of V,, will suddenly discharge through the squib 27, igniting it and thus actuating the fuze.

While the circuit above disclosed is the one at present preferred, because it utilizes existing components with a minimum of changes, yet further advantages may be attained by means of relatively slight modifications, as will now be explained.

it will be understood that a proximity fuse is necessarily a small, compact device and therefore the space therein is very limited. Elimination of the amplifier releases the space ordinarily required by two vacuum tubes, and numerous resistors and capacitors, with their connecting wires. It furthermore reduces the current-output size of the A- and B-batteries required, since only two tubes remain tobe energized, thus making it possible to reduce the electrode area.

This in turn permits increasing the number of electrodes in the B-battery that can be accommodated in the newly available space, so that a higher B-voltage may be secured.

An incidental advantage is also that the cost of the fuze is reduced materially by reducing the number of relatively expensive tubes and other components required.

The sole purpose of resistor 28 is to provide a reduced bias on the thyratron grid, while using the standard C-battery, giving a 6.5 volt bias. Therefore if a thyratron operating at -6.5 volts normal bias is substituted for V, this resistor may be omitted entirely. An equivalent result could also be obtained with the present thyratron V by removing one cell from the Obattery.

The resistor 30 is provided solely to reduce the voltage applied to the anode of V, to 90 volts, to match the available type of thyratron. Redesign of the thyratron to operate at 180 volts would eliminate the need for resistor 30 and also make it possible to reduce the capacitance of capacitor 26 very materially.

Thus with suitably rated thyratrons and/or C-batteries, the circuit could be simplified further.

While the increase in the time of response brought about by the increase of the number of rectifying stages may be a disadvantage in certain cases, it has one desireable effect, namely, it makes the fame less sensitive to premature actuation by adventitious radio signals and thus improves its safety and reliability.

In general it may be stated that fuzes made in accordance with the present invention have the advantages of simplicity, compactness, relatively low cost, and greater safety and reliability.

We claim:

I. In a proximity fuze, a receiving circuit including a detector tube, a battery supplying high-potential direct current to said detector tube, voltage rectifying and multiplying means comprising a conductor and a number of rectifiers connected therein in the same sense, in series, a number of capacitors at least equal to the number of rectifiers, a pair of additional conductors, one of which is grounded, connections applying the output potential of said detector tube across said last-named conductors, and branch circuits each containing one of the capacitors, each branch circuit being connected at one end to the first conductor at a point between two consecutive rectifiers, and the other ends of alternate branch circuits being connected to corresponding ones of said other conductors, whereby the successive capacitors become charged to progressively higher voltages, an electrically actuated detonator, a firing capacitor for applying actuating energy to said detonator, a voltage divider for charging said capacitor to a potential less than the battery potential, a thyratron controlling the discharge of said firing capacitor, and means for maintaining the thyratron grid sufficiently negative to prevent firing, the last capacitor being connected to said grid, to cause the thyratron to fire when said capacitor acquires suflicient charge to reduce the grid bias below the cutofi point' 2. In a proximity fume, an oscillator-detector tube, a highvoltage direct current source energizing said tube, a voltagerectifying and multiplying circuit connected to be energized by the output of said detector tube, a detonator, a capacitor for supplying activating energy to said detonator, a voltage divider charging said capacitor from said source of potential at a potential less than the terminal potential of said source, a thyratron tube controlling the discharge of said capacitor, connections applying a negative bias to maintain said thyratron tube nonconducting, and connections applying the output potential of said voltage-rectifying and multiplying circuit in opposition to said bias for causing said thyratron tube to fire. 

1. In a proximity fuze, a receiving circuit including a detector tube, a battery supplying high-potential direct current to said detector tube, voltage rectifying and multiplying means comprising a conductor and a number of rectifiers connected therein in the same sense, in series, a number of capacitors at least equal to the number of rectifiers, a pair of additional conductors, one of which is grounded, connections applying the output potential of said detector tube across said last-named conductors, and branch circuits each containing one of the capacitors, each branch circuit being connected at one end to the first conductor at a point between two consecutive rectifiers, and the other ends of alternate branch circuits being connected to corresponding ones of said other conductors, whereby the successive capacitors become charged to progressively higher voltages, an electrically actuated detonator, a firing capacitor for applying actuating energy to said detonator, a voltage divider for charging said capacitor to a potential less than the battery potential, a thyratron controlling the discharge of said firing capacitor, and means for maintaining the thyratron grid sufficiently negative to prevent firing, the last capacitor being connected to said grid, to cause the thyratron to fire when said capacitor acquires sufficient charge to reduce the grid bias below the cutoff point.
 2. In a proximity fuze, an oscillator-detector tube, a high-voLtage direct current source energizing said tube, a voltage-rectifying and multiplying circuit connected to be energized by the output of said detector tube, a detonator, a capacitor for supplying activating energy to said detonator, a voltage divider charging said capacitor from said source of potential at a potential less than the terminal potential of said source, a thyratron tube controlling the discharge of said capacitor, connections applying a negative bias to maintain said thyratron tube nonconducting, and connections applying the output potential of said voltage-rectifying and multiplying circuit in opposition to said bias for causing said thyratron tube to fire. 